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VALVE Magazine
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Tech tips and other unsolicited advice.
From VALVE Volume 2 Number 6 June 1995


  My experience this month with a Marantz amp and preamp gets my head spinning about the idea of paying a ton of money for something that you don't dare service for fear of terminating its investment potential. Alas, I will never make a fortune by selling off my collection of rare audio wonders, untouched by human hands. If I buy 'em, I just gotta play with 'em.

Witness here then a few suggestions for pieces to buy for hacking purposes, that is, stuff that isn't worth too much, but has lots of potential (kinda like me):


Anything but the super rare Mark VI is fair game for hacking. Stereo 70's are a great amp to learn about tubes on, and there isn't a simpler preamp around than a PAS. If you feel adventurous, an FM-3 might be a good first tuner hack. Although people try to get a bit of a high price for them, I think Mark Ill's are a legitimate hack candidate too. There's still plenty around, and there's definitely more good music to be gotten out of a pair of Ill's than from a 70.


H.H. Scott
If you don't insist on separate components, Scott integrated amps are another plentiful source of audio potential. The 222 and 299 both use 6BQ5/7189 family tubes which are relatively cheap and plentiful, while the later 299 variants and the kit sibling LK-72 use the now extinct 7591. 1 think this is just fine, as the 222/299 is a much cleaner, open sounding amp, while 7591 amps sounds a little grundgy and bass heavy to me. Integrated amps are a little more intimidating as a first project, due to space limitations, and the added complexity of having to redo a preamp and amp at the same time. On the other hand, you know your amp and preamp will work together very nicely, and interconnects wont be a problem!

Scott separates don't particularly strike me as great mod material, but I guess one could play with a 3508 tuner, as they are fairly common. The LC -21 preamp is a very nice unit, but I'm not sure they are common enough to hack up, and Scott power amps are  really hard to find.


The best candidates for heavy mods from Fisherwould have to be the receiven. The best receiver is the 500-C. The only problem is those stupid 7591s.

I haven't tried it yet, but I suspedthe KM-60 tuner would be lots of fun to hack. It seems to have the right stuff, and they aren't worth much. I even thought about combining parts from two to get an extra tuned RF stage and more IF stages, ala FM-1000.

As with Scott, the separates are getting a little too rare to hack up. The integrateds tend to use weird output tubes like the receivers, so they may not be a good choice for hacking either.



The HF-20 gets cut up a lot here in the northwest. As a mono integrated amp, it's not very desirable, folks say the iron is very nice, and you can still find them pretty cheap. The HF-81 is another nice 6BQ5 type integrated amp that would make a good project. The bigger Eico integrateds use rare tubes like 7591 s and 7247s so they could be tough to play with. Only a total idiot would do a major mod to an HF-60, and other big Eico power amps should probably be treated the same way. Just restore them nicely and enjoy.


Heathkits are close to Dynas for hackability. The best amp candidates are the W-4 and W-5. Both are plentiful, roomy, and well endowed with good iron. The Heathkit WA-P series preamps are considered worthless by most collectors as they need external power, but if you really want to play, they might be a good starting point. It's probably not a good idea to hack up an XO-1 crossover. These are getting pretty collectible. W-11s,2's and 3's are probably better left stock, as they are going up in value, too. Don't even think of wrecking a W-6!


Harmon Kardon
The Citation II amp is a true collector's item these days, which is too bad, 'cause I'd like to try a triode input/driver stage. The Citation I preamp is cheap because it's so complicated that people are scared of them. It's actually a very nice preamp, and can be selectively restored in the circuits which are normally active (a lot of stuff, like the tone control, is switched out of the circuit and thus does not affect sound unless switched in). The Citation Ill-X is my choice for a great sounding tuner that's not so collectible as to be untouchable. Citation IV's and V's are kinda scarce too, but it would probably be better to hack these than 1's and 11's. Some say the IV sounds better than a I.

An HK-250 might make a good mod project, as might some of the integrated stuff, but watch out for weird tubes. As usual, don't take any of this too seriously. If your HF-60 uses 300B1s, cool, I'd like to hear it! If you think a Stereo 70 is perfect in stock form, enjoy.

However, if you turned your Marantz 9's into plant stands, don't call us, we'll call
























































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